// Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
//
// Portions Copyright 2017 The Chromium OS Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE-BSD-3-Clause file.
//
// Copyright © 2019 Intel Corporation
//
// SPDX-License-Identifier: Apache-2.0 AND BSD-3-Clause
//

use std::os::unix::thread::JoinHandleExt;
use std::sync::atomic::{AtomicBool, Ordering};
use std::sync::{Arc, Barrier, Mutex, RwLock, Weak};
use std::thread;
use std::{fmt, io, result};

use libc::{c_void, siginfo_t};

use crate::device_manager::DeviceManager;

use devices::{ioapic, BusDevice};
use kvm_bindings::CpuId;
use kvm_ioctls::*;

use vm_memory::{Address, GuestAddress, GuestMemoryMmap};

use vmm_sys_util::eventfd::EventFd;
use vmm_sys_util::signal::{register_signal_handler, validate_signal_num};

const VCPU_RTSIG_OFFSET: i32 = 0;

// Debug I/O port
#[cfg(target_arch = "x86_64")]
const DEBUG_IOPORT: u16 = 0x80;
const DEBUG_IOPORT_PREFIX: &str = "Debug I/O port";

/// Debug I/O port, see:
/// https://www.intel.com/content/www/us/en/support/articles/000005500/boards-and-kits.html
///
/// Since we're not a physical platform, we can freely assign code ranges for
/// debugging specific parts of our virtual platform.
pub enum DebugIoPortRange {
    Firmware,
    Bootloader,
    Kernel,
    Userspace,
    Custom,
}

impl DebugIoPortRange {
    fn from_u8(value: u8) -> DebugIoPortRange {
        match value {
            0x00..=0x1f => DebugIoPortRange::Firmware,
            0x20..=0x3f => DebugIoPortRange::Bootloader,
            0x40..=0x5f => DebugIoPortRange::Kernel,
            0x60..=0x7f => DebugIoPortRange::Userspace,
            _ => DebugIoPortRange::Custom,
        }
    }
}

impl fmt::Display for DebugIoPortRange {
    fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
        match self {
            DebugIoPortRange::Firmware => write!(f, "{}: Firmware", DEBUG_IOPORT_PREFIX),
            DebugIoPortRange::Bootloader => write!(f, "{}: Bootloader", DEBUG_IOPORT_PREFIX),
            DebugIoPortRange::Kernel => write!(f, "{}: Kernel", DEBUG_IOPORT_PREFIX),
            DebugIoPortRange::Userspace => write!(f, "{}: Userspace", DEBUG_IOPORT_PREFIX),
            DebugIoPortRange::Custom => write!(f, "{}: Custom", DEBUG_IOPORT_PREFIX),
        }
    }
}

#[derive(Debug)]
pub enum Error {
    /// Cannot open the VCPU file descriptor.
    VcpuFd(kvm_ioctls::Error),

    /// Cannot run the VCPUs.
    VcpuRun(kvm_ioctls::Error),

    /// Cannot spawn a new vCPU thread.
    VcpuSpawn(io::Error),

    #[cfg(target_arch = "x86_64")]
    /// Error configuring the general purpose registers
    REGSConfiguration(arch::x86_64::regs::Error),

    #[cfg(target_arch = "x86_64")]
    /// Error configuring the special registers
    SREGSConfiguration(arch::x86_64::regs::Error),

    #[cfg(target_arch = "x86_64")]
    /// Error configuring the floating point related registers
    FPUConfiguration(arch::x86_64::regs::Error),

    /// The call to KVM_SET_CPUID2 failed.
    SetSupportedCpusFailed(kvm_ioctls::Error),

    #[cfg(target_arch = "x86_64")]
    /// Cannot set the local interruption due to bad configuration.
    LocalIntConfiguration(arch::x86_64::interrupts::Error),

    #[cfg(target_arch = "x86_64")]
    /// Error configuring the MSR registers
    MSRSConfiguration(arch::x86_64::regs::Error),

    /// Unexpected KVM_RUN exit reason
    VcpuUnhandledKvmExit,

    /// Failed to join on vCPU threads
    ThreadCleanup,

    /// Cannot add legacy device to Bus.
    BusError(devices::BusError),

    /// Failed to allocate IO port
    AllocateIOPort,

    /// Asking for more vCPUs that we can have
    DesiredVCPUCountExceedsMax,
}
pub type Result<T> = result::Result<T, Error>;

#[allow(dead_code)]
#[derive(Copy, Clone)]
enum CpuidReg {
    EAX,
    EBX,
    ECX,
    EDX,
}

pub struct CpuidPatch {
    pub function: u32,
    pub index: u32,
    pub flags_bit: Option<u8>,
    pub eax_bit: Option<u8>,
    pub ebx_bit: Option<u8>,
    pub ecx_bit: Option<u8>,
    pub edx_bit: Option<u8>,
}

impl CpuidPatch {
    fn set_cpuid_reg(
        cpuid: &mut CpuId,
        function: u32,
        index: Option<u32>,
        reg: CpuidReg,
        value: u32,
    ) {
        let entries = cpuid.as_mut_slice();

        for entry in entries.iter_mut() {
            if entry.function == function && (index == None || index.unwrap() == entry.index) {
                match reg {
                    CpuidReg::EAX => {
                        entry.eax = value;
                    }
                    CpuidReg::EBX => {
                        entry.ebx = value;
                    }
                    CpuidReg::ECX => {
                        entry.ecx = value;
                    }
                    CpuidReg::EDX => {
                        entry.edx = value;
                    }
                }
            }
        }
    }

    pub fn patch_cpuid(cpuid: &mut CpuId, patches: Vec<CpuidPatch>) {
        let entries = cpuid.as_mut_slice();

        for entry in entries.iter_mut() {
            for patch in patches.iter() {
                if entry.function == patch.function && entry.index == patch.index {
                    if let Some(flags_bit) = patch.flags_bit {
                        entry.flags |= 1 << flags_bit;
                    }
                    if let Some(eax_bit) = patch.eax_bit {
                        entry.eax |= 1 << eax_bit;
                    }
                    if let Some(ebx_bit) = patch.ebx_bit {
                        entry.ebx |= 1 << ebx_bit;
                    }
                    if let Some(ecx_bit) = patch.ecx_bit {
                        entry.ecx |= 1 << ecx_bit;
                    }
                    if let Some(edx_bit) = patch.edx_bit {
                        entry.edx |= 1 << edx_bit;
                    }
                }
            }
        }
    }
}

/// A wrapper around creating and using a kvm-based VCPU.
pub struct Vcpu {
    fd: VcpuFd,
    id: u8,
    io_bus: Arc<devices::Bus>,
    mmio_bus: Arc<devices::Bus>,
    ioapic: Option<Arc<Mutex<ioapic::Ioapic>>>,
    vm_ts: std::time::Instant,
}

impl Vcpu {
    /// Constructs a new VCPU for `vm`.
    ///
    /// # Arguments
    ///
    /// * `id` - Represents the CPU number between [0, max vcpus).
    /// * `vm` - The virtual machine this vcpu will get attached to.
    pub fn new(
        id: u8,
        fd: &Arc<VmFd>,
        io_bus: Arc<devices::Bus>,
        mmio_bus: Arc<devices::Bus>,
        ioapic: Option<Arc<Mutex<ioapic::Ioapic>>>,
        creation_ts: std::time::Instant,
    ) -> Result<Self> {
        let kvm_vcpu = fd.create_vcpu(id).map_err(Error::VcpuFd)?;
        // Initially the cpuid per vCPU is the one supported by this VM.
        Ok(Vcpu {
            fd: kvm_vcpu,
            id,
            io_bus,
            mmio_bus,
            ioapic,
            vm_ts: creation_ts,
        })
    }

    /// Configures a x86_64 specific vcpu and should be called once per vcpu from the vcpu's thread.
    ///
    /// # Arguments
    ///
    /// * `machine_config` - Specifies necessary info used for the CPUID configuration.
    /// * `kernel_start_addr` - Offset from `guest_mem` at which the kernel starts.
    /// * `vm` - The virtual machine this vcpu will get attached to.
    pub fn configure(
        &mut self,
        kernel_start_addr: GuestAddress,
        vm_memory: &Arc<RwLock<GuestMemoryMmap>>,
        cpuid: CpuId,
    ) -> Result<()> {
        let mut cpuid = cpuid;
        CpuidPatch::set_cpuid_reg(&mut cpuid, 0xb, None, CpuidReg::EDX, u32::from(self.id));
        self.fd
            .set_cpuid2(&cpuid)
            .map_err(Error::SetSupportedCpusFailed)?;

        arch::x86_64::regs::setup_msrs(&self.fd).map_err(Error::MSRSConfiguration)?;
        // Safe to unwrap because this method is called after the VM is configured
        arch::x86_64::regs::setup_regs(
            &self.fd,
            kernel_start_addr.raw_value(),
            arch::x86_64::layout::BOOT_STACK_POINTER.raw_value(),
            arch::x86_64::layout::ZERO_PAGE_START.raw_value(),
        )
        .map_err(Error::REGSConfiguration)?;
        arch::x86_64::regs::setup_fpu(&self.fd).map_err(Error::FPUConfiguration)?;
        arch::x86_64::regs::setup_sregs(&vm_memory.read().unwrap(), &self.fd)
            .map_err(Error::SREGSConfiguration)?;
        arch::x86_64::interrupts::set_lint(&self.fd).map_err(Error::LocalIntConfiguration)?;
        Ok(())
    }

    /// Runs the VCPU until it exits, returning the reason.
    ///
    /// Note that the state of the VCPU and associated VM must be setup first for this to do
    /// anything useful.
    pub fn run(&self) -> Result<bool> {
        match self.fd.run() {
            Ok(run) => match run {
                VcpuExit::IoIn(addr, data) => {
                    self.io_bus.read(u64::from(addr), data);
                    Ok(true)
                }
                VcpuExit::IoOut(addr, data) => {
                    if addr == DEBUG_IOPORT && data.len() == 1 {
                        self.log_debug_ioport(data[0]);
                    }
                    self.io_bus.write(u64::from(addr), data);
                    Ok(true)
                }
                VcpuExit::MmioRead(addr, data) => {
                    self.mmio_bus.read(addr as u64, data);
                    Ok(true)
                }
                VcpuExit::MmioWrite(addr, data) => {
                    self.mmio_bus.write(addr as u64, data);
                    Ok(true)
                }
                VcpuExit::IoapicEoi(vector) => {
                    if let Some(ioapic) = &self.ioapic {
                        ioapic.lock().unwrap().end_of_interrupt(vector);
                    }
                    Ok(true)
                }
                VcpuExit::Shutdown => {
                    // Triple fault to trigger a reboot
                    Ok(false)
                }
                r => {
                    error!("Unexpected exit reason on vcpu run: {:?}", r);
                    Err(Error::VcpuUnhandledKvmExit)
                }
            },

            Err(ref e) => match e.errno() {
                libc::EAGAIN | libc::EINTR => Ok(true),
                _ => {
                    error!("VCPU {:?} error {:?}", self.id, e);
                    Err(Error::VcpuUnhandledKvmExit)
                }
            },
        }
    }

    // Log debug io port codes.
    fn log_debug_ioport(&self, code: u8) {
        let ts = self.vm_ts.elapsed();

        debug!(
            "[{} code 0x{:x}] {}.{:>06} seconds",
            DebugIoPortRange::from_u8(code),
            code,
            ts.as_secs(),
            ts.as_micros()
        );
    }
}

pub struct CpuManager {
    boot_vcpus: u8,
    max_vcpus: u8,
    io_bus: Weak<devices::Bus>,
    mmio_bus: Arc<devices::Bus>,
    ioapic: Option<Arc<Mutex<ioapic::Ioapic>>>,
    vm_memory: Arc<RwLock<GuestMemoryMmap>>,
    cpuid: CpuId,
    fd: Arc<VmFd>,
    vcpus_kill_signalled: Arc<AtomicBool>,
    vcpus_pause_signalled: Arc<AtomicBool>,
    reset_evt: EventFd,
    vcpu_states: Vec<VcpuState>,
    selected_cpu: u8,
}

const CPU_ENABLE_FLAG: usize = 0;

const CPU_STATUS_OFFSET: u64 = 4;
const CPU_SELECTION_OFFSET: u64 = 0;

impl BusDevice for CpuManager {
    fn read(&mut self, _base: u64, offset: u64, data: &mut [u8]) {
        match offset {
            CPU_STATUS_OFFSET => {
                if self.selected_cpu < self.present_vcpus() {
                    let state = &self.vcpu_states[usize::from(self.selected_cpu)];
                    if state.active() {
                        data[0] |= 1 << CPU_ENABLE_FLAG;
                    }
                }
            }
            _ => {
                warn!(
                    "Unexpected offset for accessing CPU manager device: {:#}",
                    offset
                );
            }
        }
    }

    fn write(&mut self, _base: u64, offset: u64, data: &[u8]) {
        match offset {
            CPU_SELECTION_OFFSET => {
                self.selected_cpu = data[0];
            }
            _ => {
                warn!(
                    "Unexpected offset for accessing CPU manager device: {:#}",
                    offset
                );
            }
        }
    }
}

struct VcpuState {
    handle: Option<thread::JoinHandle<()>>,
}

impl VcpuState {
    fn active(&self) -> bool {
        self.handle.is_some()
    }

    fn signal_thread(&self) {
        if let Some(handle) = self.handle.as_ref() {
            let signum = validate_signal_num(VCPU_RTSIG_OFFSET, true).unwrap();
            unsafe {
                libc::pthread_kill(handle.as_pthread_t(), signum);
            }
        }
    }

    fn join_thread(&mut self) -> Result<()> {
        if let Some(handle) = self.handle.take() {
            handle.join().map_err(|_| Error::ThreadCleanup)?
        }

        Ok(())
    }

    fn unpark_thread(&self) {
        if let Some(handle) = self.handle.as_ref() {
            handle.thread().unpark()
        }
    }
}

impl CpuManager {
    pub fn new(
        boot_vcpus: u8,
        max_vcpus: u8,
        device_manager: &DeviceManager,
        guest_memory: Arc<RwLock<GuestMemoryMmap>>,
        fd: Arc<VmFd>,
        cpuid: CpuId,
        reset_evt: EventFd,
    ) -> Result<Arc<Mutex<CpuManager>>> {
        let cpu_manager = Arc::new(Mutex::new(CpuManager {
            boot_vcpus,
            max_vcpus,
            io_bus: Arc::downgrade(&device_manager.io_bus().clone()),
            mmio_bus: device_manager.mmio_bus().clone(),
            ioapic: device_manager.ioapic().clone(),
            vm_memory: guest_memory,
            cpuid,
            fd,
            vcpus_kill_signalled: Arc::new(AtomicBool::new(false)),
            vcpus_pause_signalled: Arc::new(AtomicBool::new(false)),
            vcpu_states: Vec::with_capacity(max_vcpus as usize),
            reset_evt,
            selected_cpu: 0,
        }));

        device_manager
            .allocator()
            .lock()
            .unwrap()
            .allocate_io_addresses(Some(GuestAddress(0x0cd8)), 0x8, None)
            .ok_or(Error::AllocateIOPort)?;

        cpu_manager
            .lock()
            .unwrap()
            .io_bus
            .upgrade()
            .unwrap()
            .insert(cpu_manager.clone(), 0x0cd8, 0xc)
            .map_err(Error::BusError)?;

        Ok(cpu_manager)
    }

    fn activate_vcpus(&mut self, desired_vcpus: u8, entry_addr: GuestAddress) -> Result<()> {
        if desired_vcpus > self.max_vcpus {
            return Err(Error::DesiredVCPUCountExceedsMax);
        }

        let creation_ts = std::time::Instant::now();
        let vcpu_thread_barrier = Arc::new(Barrier::new(
            (desired_vcpus - self.present_vcpus() + 1) as usize,
        ));

        for cpu_id in self.present_vcpus()..desired_vcpus {
            let ioapic = if let Some(ioapic) = &self.ioapic {
                Some(ioapic.clone())
            } else {
                None
            };

            let mut vcpu = Vcpu::new(
                cpu_id,
                &self.fd,
                self.io_bus.clone().upgrade().unwrap(),
                self.mmio_bus.clone(),
                ioapic,
                creation_ts,
            )?;
            vcpu.configure(entry_addr, &self.vm_memory, self.cpuid.clone())?;

            let vcpu_thread_barrier = vcpu_thread_barrier.clone();

            let reset_evt = self.reset_evt.try_clone().unwrap();
            let vcpu_kill_signalled = self.vcpus_kill_signalled.clone();
            let vcpu_pause_signalled = self.vcpus_pause_signalled.clone();

            let handle = Some(
                thread::Builder::new()
                    .name(format!("vcpu{}", vcpu.id))
                    .spawn(move || {
                        unsafe {
                            extern "C" fn handle_signal(_: i32, _: *mut siginfo_t, _: *mut c_void) {
                            }
                            // This uses an async signal safe handler to kill the vcpu handles.
                            register_signal_handler(
                                VCPU_RTSIG_OFFSET,
                                vmm_sys_util::signal::SignalHandler::Siginfo(handle_signal),
                                true,
                                0,
                            )
                            .expect("Failed to register vcpu signal handler");
                        }

                        // Block until all CPUs are ready.
                        vcpu_thread_barrier.wait();

                        loop {
                            // vcpu.run() returns false on a KVM_EXIT_SHUTDOWN (triple-fault) so trigger a reset
                            match vcpu.run() {
                                Err(e) => {
                                    error!("VCPU generated error: {:?}", e);
                                    break;
                                }
                                Ok(true) => {}
                                Ok(false) => {
                                    reset_evt.write(1).unwrap();
                                    break;
                                }
                            }

                            // We've been told to terminate
                            if vcpu_kill_signalled.load(Ordering::SeqCst) {
                                break;
                            }

                            // If we are being told to pause, we park the thread
                            // until the pause boolean is toggled.
                            // The resume operation is responsible for toggling
                            // the boolean and unpark the thread.
                            // We enter a loop because park() could spuriously
                            // return. We will then park() again unless the
                            // pause boolean has been toggled.
                            while vcpu_pause_signalled.load(Ordering::SeqCst) {
                                thread::park();
                            }
                        }
                    })
                    .map_err(Error::VcpuSpawn)?,
            );

            self.vcpu_states.push(VcpuState { handle });
        }

        // Unblock all CPU threads.
        vcpu_thread_barrier.wait();
        Ok(())
    }

    // Starts all the vCPUs that the VM is booting with. Blocks until all vCPUs are running.
    pub fn start_boot_vcpus(&mut self, entry_addr: GuestAddress) -> Result<()> {
        self.activate_vcpus(self.boot_vcpus(), entry_addr)
    }

    pub fn shutdown(&mut self) -> Result<()> {
        // Tell the vCPUs to stop themselves next time they go through the loop
        self.vcpus_kill_signalled.store(true, Ordering::SeqCst);

        // Signal to the spawned threads (vCPUs and console signal handler). For the vCPU threads
        // this will interrupt the KVM_RUN ioctl() allowing the loop to check the boolean set
        // above.
        for state in self.vcpu_states.iter() {
            state.signal_thread();
        }

        // Wait for all the threads to finish. This removes the state from the vector.
        for mut state in self.vcpu_states.drain(..) {
            state.join_thread()?;
        }

        Ok(())
    }

    pub fn pause(&self) -> Result<()> {
        // Tell the vCPUs to pause themselves next time they exit
        self.vcpus_pause_signalled.store(true, Ordering::SeqCst);

        // Signal to the spawned threads (vCPUs and console signal handler). For the vCPU threads
        // this will interrupt the KVM_RUN ioctl() allowing the loop to check the boolean set
        // above.
        for state in self.vcpu_states.iter() {
            state.signal_thread();
        }

        Ok(())
    }

    pub fn resume(&self) -> Result<()> {
        // Toggle the vCPUs pause boolean
        self.vcpus_pause_signalled.store(false, Ordering::SeqCst);

        // Unpark all the VCPU threads.
        // Once unparked, the next thing they will do is checking for the pause
        // boolean. Since it'll be set to false, they will exit their pause loop
        // and go back to vmx root.
        for state in self.vcpu_states.iter() {
            state.unpark_thread();
        }
        Ok(())
    }

    pub fn boot_vcpus(&self) -> u8 {
        self.boot_vcpus
    }

    pub fn max_vcpus(&self) -> u8 {
        self.max_vcpus
    }

    fn present_vcpus(&self) -> u8 {
        self.vcpu_states.len() as u8
    }
}